Field comparison of cyclonic separator and mass inertial impactor for PM10 monitoring

Monitoring of ambient PM10 concentrations was carried out using two co-located samplers at 10 different locations over the three seasons (summer, winter and post-monsoon) in Delhi, India. The samplers used for the study were the high volume sampler fitted with a cyclone (commonly known in India as respirable particulate matter sampler or RPM sampler), and a 4-channel speciation sampler (4-SS). The RPM sampler separates the PM10 fraction using centrifugal inertia while the 4-SS separates them using the principle of mass inertial impaction. Comparison of the measured data are made using different graphical techniques and statistical analysis, comprising classical two tailed paired t-test and the criteria recommended by the European Commission working group on particulate matter. The PM10 data monitored by both the samplers showed good overall correlations for the entire data set, with a regression co-efficient value of 0.61. Results indicated that inertial impaction based 4-SS consistently measures higher PM10 concentration compared with the cyclone fitted RPM sampler. Such results were valid for 81% of the total data set and this difference in measured concentrations was ∼66% in the regulatory limit value ranges. Both the samplers have their merits and limitations and hence a conscious choice and appropriate data correction is needed when deploying them for scientific and regulatory monitoring purposes.